Comcast Corp., of Philadelphia, said on Monday that it has ramped up its marketing efforts in New England to sell phone service to businesses with fewer than 21 employees.

Dan Sullivan, Comcast’s vice president of business services for Southeastern Massachusetts, said the company began actively selling phone service to small businesses in the region last fall. He said Comcast views the market as a natural extension of its focus on providing TV, voice and Internet services to residential customers.

“It’s a great opportunity for us to grow,” Sullivan said. “(Small businesses) have been somewhat underserved by the legacy (phone service) carriers.”

Sullivan said that for now, Comcast will provide phone services to larger businesses on a case-by-case basis. He said he expects Comcast will eventually sell voice options to that market.

Sullivan said that basic phone service for small businesses, with unlimited calling in the U.S., sells for $50 a month per line.

Bundled packages that include TV and high-speed Internet service are available at promotional rates for $100 a month and $150 a month; the more expensive option includes a faster Internet connection and more phone lines, Sullivan said. The promotional rates can be locked in for up to three years, he said.

Jim Hughes, a spokesman for Comcast, said the company has doubled its business services staff in the state during the past year in preparation for the launch. He declined to provide specific numbers, though, about how many people have been hired here.

Comcast executives said they believed it was important to hire a number of local salespeople – as opposed to centralized call center workers – so they could provide personalized service, Sullivan said. “We’re putting a lot of feet on the street to make sure we get to know and understand the various business communities,” said Sullivan, who works in Comcast’s Plymouth office.

Verizon, the state’s largest provider of local phone service, remains focused on marketing services to small businesses as well, according to Verizon spokesman Phil Santoro. He said the company will continue to market bundled packages aggressively to small business customers in the area despite Comcast’s launch.